Low thermal mass gc module

ABSTRACT

A system and method for performing field-portable GC/MS measurements for the rapid sampling and measurement of high temperature boiling semi-volatile organic compounds in environmental samples, wherein other column bundles have cold spots that may prevent high temperature boiling semi-volatile components from eluting the GC column, this new design may eliminate those cold spots on the GC column.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.15/636,362, filed Jun. 28, 2017, which claims priority to U.S.Provisional Patent Application No. 62/355,761, filed Jun. 28, 2016, thedisclosures of both of which are hereby incorporated by reference intheir entireties.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to the applicability of field-portablegas chromatograph/mass spectrometer (GC/MS) for the rapid sampling andmeasurement of high temperature boiling semi-volatile organic compounds.

Description of Related Art

Over the years, many types of analytical instruments have been reducedto a portable or hand-held format to be used in the field, includingX-ray Fluorescence Analyzers, Laser-induced Breakdown Spectroscopy,Raman Spectroscopy, Fourier Transform Infrared Spectroscopy andNear-infrared Spectroscopy analyzers. However, shrinking a GC/MS to afield-portable configuration, while maintaining laboratory analyticalperformance, is a much greater challenge. Most of the previous attemptshave utilized “point-and-shoot” approaches which have not required anytype of sample preparation or sample introduction accessories. For thatreason, the practical value of a field-portable instrument is reducedsignificantly if it necessitates complex sample preparation or delicateprocedures are required to introduce the sample into the instrument.

Furthermore, presently available column bundles may have cold spots thatprevent high temperature boiling semi-volatile compounds from elutingthe GC column. Accordingly, it would be an advantage over the state ofthe art to have a field-portable GC/MS instrument that is capable ofeliminating the cold spots.

For example, FIG. 1 illustrates a low thermal mass (LTM) column bundle,or GC module, that is formed into a toroidal bundle 12 and surrounded byfoil 14 as known in the prior art. A quarter is shown in theillustration for size comparison purposes only. FIG. 1 shows aninsulated GC column 10 that is coiled multiple times inside the toroidalbundle 12. Also interspersed within the toroidal bundle 12 is aninsulated heating wire 16 and a temperature sensor 18, both of which arealso coiled within the conductive foil 14. The positioning of theinsulated GC column 10, the temperature sensor 18 and the insulatedheating wire 16 may be random or pseudo-random as shown.

It is well recognized that high-temperature program methods are normallyrequired for the determination of semi-volatile analytes such as PAHsand pesticides in various sample matrices. However, when using the priorart LTM column technology such as the toroidal bundle 12 shown in FIG. 1, it is fairly typical to get poor peak shapes and resolution at theseelevated temperatures. This problem is mainly caused by the realtemperature in the GC column 10 not matching the values that were set inthe method, due to the cooler sites 20 existing on the GC column,especially in areas that are located near to the conductive foil 14. Inaddition, there may also be cooler sites 20 on the GC column 10 whichare not close to where the temperature sensors 18 are disposed. Thisphenomenon is exemplified in FIG. 1 , which shows an example of onlysome of the possible cooler sites 20 inside the toroidal bundle 12.

BRIEF SUMMARY OF THE INVENTION

A first embodiment of the present invention includes a system and methodfor performing field-portable GC/MS measurements for the rapid samplingand measurement of high temperature boiling semi-volatile organiccompounds in environmental samples, wherein cold spots in capillarytubing of the GC column that may prevent high temperature boilingsemi-volatile components from eluting the GC column may be eliminatedfrom a new design of a low thermal mass (LTM) GC module.

These and other objects, features, advantages and alternative aspects ofthe present invention will become apparent to those skilled in the artfrom a consideration of the following detailed description taken incombination with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows possible cooler sites experienced with standard LTM columnbundle technology of the prior art.

FIG. 2 is a perspective view of the first embodiment of a low thermalmass GC module for use in a field-portable GC/MS that minimizes coolspots in capillary tubing to enable rapid sampling and measurement ofhigh temperature boiling semi-volatile organic compounds.

FIG. 3 is a cross-sectional view of the LTM GC module shown in FIG. 2 .

FIG. 4A is a perspective and exploded view of a LTM heater columnassembly used in the LTM GC module.

FIG. 4B is a perspective view of the assembled LTM heater columnassembly shown in FIG. 4A.

FIG. 5A is a perspective and exploded view of the various componentsthat are assembled to form the LTM GC module.

FIG. 5B is a perspective view of the assembled LTM GC module shown inFIG. 5A.

FIG. 6A is a perspective and exploded view of the components of thetemperature sensor.

FIG. 6B is a perspective view of the assembled temperature sensor ofFIG. 6A.

FIG. 7 is a perspective view of the fully assembled LTM GC module whichhas been disposed on a mounting board.

FIG. 8 is a chromatographic comparison between a standard LTM column(red) and the new LTM column (black) described in this study for theseparation and analysis of a mix of 18 PAH compounds (labeled andidentified 1-18).

FIG. 9 is a chromatographic comparison between a standard LTM column(red) and the new LTM column (black) described in this study for theseparation and analysis of a mix of 17 organochlorine pesticidecompounds (labeled and identified 1-17).

FIG. 10 is a chromatographic comparison between a standard LTM column(black) and the new LTM column (red) described in this study for theseparation and analysis of a mix of 10 pyrethroid pesticide compoundsand three isomers (labeled and identified 1-13).

FIG. 11 illustrates that the fiber is placed half in the head space andhalf immersed into the liquid phase of the sample.

FIG. 12 illustrates a total ion chromatogram of (1) Alpha+pinene, (2)Myrcene, (3) Alpha+limonene, and (4) Isolongifolene.

FIG. 13 illustrates Calibration plots of the four terpene compounds.

FIG. 14 illustrates the sampling procedure and thermal desorption stepfor the analysis of geosmin by GC/MS.

FIG. 15 illustrates Total ion (TIC) and extracted ion chromatograms (MC)of geosmin and its MS fragments in a water sample, identified andconfirmed by the mass spectrum from the NIST reference library.

FIG. 16 illustrates the deconvoluted chromatogram and mass spectrumdemonstrating that the geosmin is well-separated using the instrument'sdeconvolution algorithm.

FIG. 17 illustrates a Total Ion Chromatogram of a 250 ppb ppm spikedsample of PAHs.

FIG. 18 illustrates the total ion chromatogram of the separation of allthe phenolic compounds in water with phenol (C6H5OH) identified with thebold red arrow.

FIG. 19 illustrates the total ion chromatogram of the separation of agroup of phthalate esters with dimethyl phthalate (C10H10O4) shown witha bold red arrow.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the drawings in which the various elementsof the present invention will be given numerical designations and inwhich the invention will be discussed so as to enable one skilled in theart to make and use the invention. It is to be understood that thefollowing description is only exemplary of the principles of the presentinvention, and should not be viewed as narrowing the claims whichfollow.

This document describes results from a field-portable GC/MS (Torion T-9,PerkinElmer Inc, Shelton, Conn.) for a wide variety of samples (gas,liquid, solid), including the analysis of high-boiling, semi-volatileorganic compounds (SVOC) with a typical analysis time of less than 10minutes.

In order to minimize cool sites within a LTM GC module as described inFIG. 1 , a new LTM GC column bundle was designed as shown in FIG. 2 .FIG. 2 shows the first embodiment of a LTM GC column 30 that uses thinaluminum covers to wrap around a single-layer ordered-arrangement GCcolumn and insulated heating wire. This column may provide identicalheat distribution while virtually eliminating or at least minimizingcooler spots along the column, thus improving the chromatographicseparation for SVOCs at the high temperature GC runs required for hightemperature boiling point compounds. The principles of this new LTM GCmodule 30 are shown in a first embodiment beginning with FIG. 2 .

FIG. 2 shows a perspective view of a first embodiment of a LTM GC module30. The LTM GC module 30 may be comprised of a LTM heater columnassembly, a LTM capillary column assembly, and a sensor assembly.

FIG. 3 is a cross-sectional view of the LTM GC module 30 shown in FIG. 2. The cross-sectional view shows the various components of the GC column30 design. The LTM GC module 30 may include an inner column ring 32, amiddle column ring 34, and an outer column ring 36. Tabs 42 may also beprovided on the Outer column ring 36 so that they may be folded over theInner column ring 32 and hold the LTM GC module together in a desiredshape. The inner column ring 32, middle column ring 34, and outer columnring 36 may be comprised of a thermally conductive material such asaluminum.

As shown, a heating wire 38 may be disposed between the inner columnring 32 and the middle column ring 34. Furthermore, a single layer ofcapillary tubing 40 may be disposed between the middle column ring 34and the outer column ring 36. A temperature sensor is not shown in thisfigure but will be shown later.

The heating wire 38 is disposed between the inner column ring 32 and themiddle column ring 34 so that there is heating of an inner surface ofthe middle column ring 34. As stated, a material is selected for themiddle column ring 34 such that heat may be uniformly transferredthrough the middle column ring 34 to an outer surface thereof.

It should be understood that the specific number of times that theheating wire 38 is wound around the inner column ring 32 is notimportant and may depend on the gauge of the heating wire 38 being used.What is important is that the heating of the inner surface of the middlecolumn ring 34 that is disposed over the heating wire 38 should besubstantially uniform. Accordingly, the number of coils of the heatingwire 38 around the inner column ring 32 may be varied from that shown inFIG. 3 . Furthermore, the heating wire 38 may overlap as long as it doesnot interfere with the uniform heating of the inner surface of themiddle column ring 34. Therefore, any overlap of the heating wire shouldalso be uniform so that the heating of the middle column ring 34 isuniform.

The heating wire may be any appropriate thickness and material. In theexample shown in FIG. 3 , the heating wire 38 is 27 AWG, but this isonly an example and should not be considered to be limiting of thethickness of heating wire that may be used.

Similarly, the LTM GC column 32 may include capillary tubing ofapproximately 0.10 mm ID and be approximately 5.5 meters in length. Itshould be understood that these dimensions are for illustration purposesonly and are not limiting of the dimensions that may be used. The GCcolumn used in a field-portable gas chromatograph/mass spectrometer(GC/MS) may only be limited by the application and the dimension of theouter column ring 36. Thus, it may that the ID and length of thecapillary tubing may be larger or smaller in order to change resolutionand sensitivity. Accordingly, the ID and length of the capillary tubingmay only be limited by the size of the inner, middle and outer columnrings 32, 34, 36 that enable the capillary tubing to be wound in asingle layer on the middle column ring. Furthermore, it should beunderstood that no such size limitations are present in a benchtopversion of the GC column.

FIG. 4A is a perspective and exploded view of the LTM heater columnassembly 50. The assembled LTM heater column assembly 50 shown in FIG.4B may be comprised of the inner column ring 32, the middle column ring34, and the heating wire 38 disposed between as shown in FIG. 4A.Heating wire sleeves 52 may be used to cover the exposed leads of theheating wire 38.

FIG. 5A is a perspective and exploded view of the LTM heater columnassembly 50, the capillary tubing 40, the outer column ring 36, a flangecover 54, and a plurality of tabs 42. The capillary tubing 40 is woundaround the outside surface of the LTM heater column assembly 50, andthen the outer column ring 36 is disposed around the capillary tubing.

FIG. 5B shows the assembled components that form the LTM GC module 30,along with a detached temperature sensor 60. The completely assembledLTM GC module 30 is shown in FIG. 2 . The temperature sensor 60 may becapable of sensing a wide range of temperatures, such as from −70 to 500degrees C. However, this temperature range should only be considered asan example and not a limitation of the first embodiment.

There are several aspects of the first embodiment shown in FIGS. 2through 5B that are important for the LTM GC module 30 to function asdesired.

In a first aspect shown in FIG. 4B, the LTM heater column assembly 50needs to provide a continuous heating surface on the outer surface ofthe middle column ring 34. The outer surface of the middle column ring34 is essentially the surface of a cylinder.

Another aspect of the first embodiment is that the outer surface of themiddle column ring 34 needs to be substantially smooth such that if aflexible object is wrapped around the middle column ring 34, it willalways make contact with the outer surface in order to provide uniformheating of an object on the outer surface.

Another aspect of the first embodiment is that the heating wire 38 thatis wound around the inner column ring 32 needs to be wound in such a waythat when the middle column ring 34 is placed around the inner columnring to enclose the heating wire between the inner and middle columnrings 32, 34, the result should be that the outer surface of the middlecolumn ring 34 is heated equally. This may be accomplished by any methodof winding the heating wire 38 around the inner column ring 32 thatallows equal heating to occur. For example, there may be equaldistribution of the heating wire 38 on the inner column ring 32. Anequal distribution may require equal spacing or elimination of allspacing between the windings of the heating wire 38.

However, it may not sufficient that the inner column ring 34 provides auniformly heated outer surface. Another aspect of the first embodimentis that the capillary tubing 40 must be wound around the middle columnring 34 in such a way that all of the capillary tubing around the middlecolumn ring is heated equally. Equal heating of the capillary tubing 40may be accomplished by winding the capillary tubing such that no portionof the capillary tubing is overlapping any other portion. Thus, if allof the capillary tubing 40 is in contact with the outer surface of themiddle column ring 34, then cold spots may be minimized. Therefore, itis likely that the capillary tubing 40 is in a single-layer arrangement.

Another aspect of the first embodiment of the present invention is thatthe temperature sensor 60 may not have to be disposed along the entirelength of the capillary tubing 40 as in the prior art shown in FIG. 1 .Because the temperature of the LTM GC module 30 may be uniform becauseof the arrangement of the heating wire 38 and the capillary tubing 40,the temperature sensor 60 may be disposed in only a single location onthe LTM GC module. In this example, the temperature sensor 60 may bedisposed on the inside of the inner column ring 32.

FIG. 6A is a perspective and exploded view of the components of thetemperature sensor 60 of the first embodiment of the invention. Thetemperature sensor 60 may include a resistance temperature detection(RTD) sensor as known to those skilled in the art. However, any suitabletemperature sensor may be used in the first embodiment of the invention.

The temperature sensor 60 may include an RTD sensor 62, a housing 64,crimp tubing 66, two hook-up wires 68 and two insulated wire sleeves 70.

FIG. 6B is a perspective view of the assembled components of thetemperature sensor 60 as used in the first embodiment.

FIG. 7 is a perspective view of the fully assembled LTM GC module 30which has been disposed on a mounting board 70. A plurality of insulatorcolumns 72 are used to hold the LTM GC module 30 above the mountingboard 70. The number of insulator columns 72 may vary and should not beconsidered to be a limitation of the first embodiment of the invention.Connectors 74 are coupled to the heating wire 38 and to the temperaturesensor 60 and may be used to send signals to and receive signals fromoff the mounting board 70.

In order for the LTM GC module 30 to be suitable for use in afield-portable GC/MS unit, the diameter of the outer column ring 36should be kept relatively small. Using capillary tubing of the sizegiven in the example, the diameter of the outer column ring 36 may be 10cm or smaller.

In a summary of the first embodiment, a heating system is taught forminimizing cold spots in capillary tubing of a column used forperforming field-portable Gas Chromatography/Mass Spectrometer (GC/MS)measurements. The components of such a heating system may include aninner cylindrical ring, a heating wire disposed around the innercylindrical ring, a middle cylindrical ring disposed around the heatingwire and the inner cylindrical ring, wherein the heating wire uniformlyheats the middle cylindrical ring, a capillary tubing used as a GCcolumn is disposed around an outer surface of the middle cylindricalring, wherein the capillary tubing does not overlap itself on the middlecylindrical ring, and an outer cylindrical ring is disposed around thecapillary tubing and the middle cylindrical ring.

The heating system may also include a temperature sensor disposed on theinner cylindrical ring to thereby enable temperature readings of theinner cylindrical ring, and thus the LTM GC column 30. In order to keepthe system for use in a field-portable GC/MS measurement system, theouter cylindrical ring may be less than 10 cm in diameter.

This document describes results from a field-portable GC/MS (Torion T-9,PerkinElmer Inc, Shelton, Conn.) for a wide variety of samples (gas,liquid, solid), including the analysis of high-boiling, semi-volatileorganic compounds (SVOC) with a typical analysis time of less than 10minutes. The semi-volatile compounds studied include: separating amixture of polycyclic aromatic hydrocarbons (PAH) with a boiling pointrange from napthalene (218° C.) to benzo perylene (550° C.);characterization of a suite of organochlorine pesticides with a boilingpoint range from dichlroan (130° C.) to deltamethrin (572° C.);quantifying a mixture of terpenes with boiling points of 155-177° C.;detecting a natural compound such as geosmin with a boiling point of270° C., which is a byproduct of bacterial activity in environmentalwater samples; analysis of PAHs in asphalt and coal tar-based gravelsamples; and screening for phenolic compounds and phthalate esters inwater, which are used in the manufacture of many plastic components.

To better understand the practical capabilities of the first embodiment,it's worth giving a brief overview of its capabilities. Although thistechnology was built for portability and speed, the gas chromatographwas designed to provide equivalent chromatographic resolution andperformance to a benchtop system. The miniature size is achieved byreplacing a conventional capillary column and convection oven with a lowthermal mass (LTM) GC column bundle using direct-contact electricalresistive heating. In this design, a small diameter, metal capillarycolumn may be bundled with resistive heating and temperature-sensingwires that may be braided together with insulator strands. This approachmay provide for more controlled heating, greater heating and coolingspeeds and very low power consumption. Because column heating requiresconsiderably less operating power than a conventional GC, longerbattery-lifetime may be experienced. With its combination of directresistive heating and rapid temperature ramp rates, the first embodimentmay separate multi-component analytes in a few minutes.

The mass spectrometer may use a toroidal ion trap configuration, whichis well-suited for miniaturization compared to other types of massspectrometers, such as conventional cylindrical ion traps or linearquadrupole traps. The novel configuration of the first embodiment mayallow for large trapping volumes despite its miniaturized size. Theresult may be high ion counts and increased sensitivity, low noiselevels and good spectral quality. The ion trap mass analyzer may beheated to ^(˜)175° C. and operate under vacuum, which may result in theelectrodes staying clean for long periods of time. This may reduce theneed for frequent maintenance, while increasing mass spectral qualityand reproducibility. Performing at an elevated temperature may also leadto long-term MS resolution stability, providing unit mass resolutionover the 45-500 amu mass range.

The sample preparation station also offers the capability of differentmodules in the field, including sample desorption (SD), heated headspace(HS), purge and trap (PT) as well as an internal standard (IS) additionmodule. It can easily be configured for specific applicationrequirements for sample preparation and analysis at the samplinglocation. It allows for transfer of air samples collected onconventional-sized collection traps to micro traps for injection intothe micro-bore capillary GC. During this desorption process, theanalytes are transferred from a conventional trap to the instrument'sneedle trap for injection into the GC-MS. The complete module can beoperated either from a laboratory gas supply (helium or nitrogen) andline power, or it can operate from battery power and an internal tank ofpressurized gas.

In addition, the use of on-board libraries can not only identify unknowntarget compounds but also allow users to custom build target compoundlibraries. This feature is supported by deconvolution algorithms toensure reliable identification of even co-eluting compounds in complexmixtures, and used in conjunction with an extensive NIST database;unknown peaks can be easily identified.

To obtain a better understanding of the practical capabilities of thefirst embodiment for the separation and analysis of semi-volatilecompounds, a comparison was made between a prior art LTM GC column andthe LTM GC column of the first embodiment for a suite of semi-volatileorganic compounds with a boiling point range of 200-570° C.

Three mixtures of semi-volatile compounds were evaluated, including 18PAHs compounds, 17 organochlorine pesticides compounds, and 10pyrethroid pesticides compounds. The same amount of each sample wasintroduced into three different systems by a solvent free, coil wirefilament (CWF) injection system, and run using exactly the same GCchromatographic separation and mass spectrometer operating conditionsshown in Table 1.

TABLE 1 Gas Chromatographic Separation Conditions Sample Delivery CoilWire Filament Injection Injection Type Split/Splitless InjectorTemperature 300° C. Transfer Line Temperature 280° C. Trap Temperature200° C. Column Technology MXT ®-5: low-polarity phase (Restek ®, StateCollege, PA) diphenyl dimethyl polysiloxane; 5 m × 0.1 mm × 4 μm InitialTemperature/Hold Time 50° C. for 10 s Temperature Ramp Rate 20° C./secFinal Temperature/Hold Time 300° C. for 125 s Mass SpectrometerOperating Conditions Mass Spectrometer Toroidal Ion Trap IonizationSource Electron Capture MS Operating Temperature 175° C. Mass Range45-500 amu Resolution <1 amu at 300 amu MS Scan Rate 10-15 scans/secDetector Electron Multiplier

The concentration of each compound in the three different mixtures isshown in in Table 2.

TABLE 2 Working Std l in MeOH, Na Component ug/mL OrganochlorinePesticide Mix 1 Aldrin 10 2 α-BHC 10 3 γ-BHC 10 4 β-BHC 10 5 δ-BHC 10 64,4′-DDD 10 7 4,4′-DDE 10 8 4,4′-DDT 10 9 Dieldrin 10 10 Endosulfan I 1011 Endosulfan II 10 12 Endosulfan Sulfate 10 13 Endrin 10 14 Endrinaldehyde 10 15 Heptachlor 10 16 Heptachlor epoxide (isomer B) 10 17Methoxychlor 10 PAH mix 1 Acenaphthene 9.93 2 Acenaphthylene 19.86 3Anthracene 1.01 4 Benz(a)anthracene 1.01 5 Benzo(a)pyrene 1.00 6Benzo(b)fluoranthene 2.03 7 Benzo(k)fluoranthene 1.01 8Benzo(g,h,i)perylene 1.98 9 Cltrysene 1.01 10 Dibenz(a,b)anthracene 2.0011 Fluoranthene 2.01 12 Dfluorene 2.03 13 Indeno(1,2,3-cd)pyrene 1.01 14Napthalene 10.01 15 Phenanthren 1.00 16 pyrene 1.00 171-Methylnaphthalene 9.95 18 2-Methylnaphthalene 9.88 Pesticide Mix 14 1Cyfluthrin 5.07 2 L-Cyhalothrin 4.98 3 Cypermethrin 5.03 4 Deltamethrin5.05 5 Dichloran 1.00 6 Fevalerate 5.03 7 Pendimethalin 1.02 8Permethrin 4.96 9 Tetrachloviep bos 0.10 10 Tefluthrin 0.98

The comparative chromatograms of each mixture can be seen in FIG. 8 (18PAH compounds, FIG. 9 (17 organochlorine pesticides), and FIG. 10 (10pyrethroid pesticides). The standard LTM column chromatograms are shownin red, while the new LTM column versions are in black.

From FIGS. 8, 9 and 10 , several observations may be made. First, peakshapes and resolution appeared to be much worse in the prior art LTM GCcolumn because it generated wider peaks with a noisier background. Next,the retention times of the peaks in the prior art LTM GC column weresubstantially longer. Also, peak intensities in the LTM GC column of thefirst embodiment were significantly higher than those in theconventional one. And finally, a standard LTM GC column could notseparate and elute components 16, 17 and 18 in the PAH mix, because oftheir very low volatility (boiling points 524-550° C.)

An analysis of a suite of different semi-volatile organic compounds,with a wide range of boing points is now provided.

Terpenes are a large class of organic compounds, produced by a varietyof plants, including conifers, hops, and cannabis with a typical boilingpoint range of 150-180° C. They are the primary constituents of theessential oils of many types of plants and flowers widely used asfragrances in perfumery, as well as for medicinal purposes. Syntheticvariations and derivatives of natural terpenes are also used for avariety of aromas and flavors used as food additives. Therefore, toexemplify the capability of this technology, four terpene compounds werespiked into 200 mL of 0.6% NaCl in water. The analytes were thenextracted using half/half solid phase micro extraction (SPME)polydimethylsiloxane/divinylbenzene (PDMS/DVB) 65 μm fibers at roomtemperature (22° C.) for 15 minutes without shaking or vibrating. Withthis sampling approach, the fiber is placed half in the head space andhalf immersed into the liquid phase of the sample, as shown in FIG. 11 .

The four terpene analytes were extracted by half/half SPME (PDMS/DVB 65μm fibers) at room temperature (22° C.) for 15 minutes, before beinginjected into the GC/MS.

This sample was then injected into the GC/MS system using similarconditions described earlier, with the exception that the finaltemperature of 280° C. was held for 50 s, making a total analysis timeof 175 s. The total ion chromatogram (TIC) of the four terpenes(Alpha+pinene, Myrcene, Alpha+limonene, and Isolongifolene), is shown inFIG. 12 .

A four-point calibration graph was generated for the four terpenecompounds. The concentrations of the standards and the respectivecalibration plots with correlation coefficients (R2) are shown in FIG.13 . It should be noted that the estimated detection limit for the fourcompounds was 20 ppt, which was based on the statistical analysis ofmultiple replicates of the lowest standard (Sample 1).

Geosmin is an organic compound produced by a variety of microorganismsand bacteria. It has a distinct earthy flavor and aroma, and isresponsible for the earthy taste of beets and the strong scent thatoccurs in the air when rain falls after a dry spell of weather. Geosminis produced by several classes of microbes, including cyanobacteria andactinobacteria, and is released when these microbes die. Communitieswhose water supplies depend on surface water can periodically experienceepisodes of unpleasant-tasting water when a sharp drop in the populationof these bacteria releases geosmin into the local water supply (9).Chemically, it is a bicyclic alcohol with a formula of C12H22O, and aderivative of decahydro naphthalene, commonly known as decalin. Itsboiling point is ^(˜)270° C.

The methodology included 20 ppt of Geosmin was spiked into 500 mLs of awater sample. Without any pretreatment step, it was then trapped onPolydimethylsiloxane (PDMS) particles (125-180 um size) packed in adeactivated stainless steel solid phase extraction (SPE) desorption tubeat ambient temperature using a flow rate of 25-35 mL/min delivered by avacuum pump. The target analyte was then transferred into a PDMS needletrap using the instrument's thermal desorber system. The desorption stepwas carried out at 200° C. at 6 mL/min for 10 min, using He carrier gas.Sample introduction into the GC-TMS using the needle trap was conductedat 270° C. for 60 s. A schematic of the sample delivery approach isshown in FIG. 14 .

The chromatographic separation conditions are shown in Table 3. Thetotal ion chromatogram (TIC) of the separation is shown in FIG. 15 ,together with extracted ion chromatogram (MC), showing the parentmolecular ion and the associated fragments of geosmin, which isconfirmed by the NIST reference mass spectrum underneath it. FIG. 16shows the deconvoluted chromatogram and mass spectrum, demonstratingthat the 20 ppt geosmin is well-separated using the instrument'sdeconvolution algorithm. Based on the statistical analysis of thegeosmin calibration, it was estimated that the detection limit was inthe order of single digit ppt levels.

TABLE 3 Split Temperature Injection Column Heaters Program TimeSpecifications Injector Ramp rate 10:1 split on Length 270% C_(x) 1°C./s 20 s 5 m Transfer Starting temperature 10:1 split off Diameter lineand hold time 250° C. 50° C. for 10 s 40 s 0.1 mm MS Trap Endtemperature and 50:1 split on Stationary phase hold time 190° C. 300° C.for 10 s 40 s MS 5 (5% phenyl 95% methyl polysiloxane) Carrier gas inlet50:1 split off pressure 26 psi 80 s

Road and parking lot surfaces are typically made from asphalt and/orcoal tar products which contain high levels of carbonaceous compounds.For this reason, it is very important to know the composition of the PAHlevels in the gravel samples used in the road surface preparationprocess. For this study, 40 g of the gravel samples were spiked withstock standard solutions to make calibration standards of 0.05, 0.25,0.5, and 1.0 ppm of the PAH analytes. The samples were then extractedwith a mixture of dichloromethane (5 mL) and water (^(˜)15 mL) by handshaking for about 2-3 min. The liquid phase was then transferred toanother vial to let the two phases separate out. For some of thesamples, pre-concentration was necessary to improve the detection. Thiswas achieved by placing 1 mL of the organic phase into a 2 mL vial andallowing the solvent to evaporate to get a suitable volume for themeasurement. A 20 μL aliquot of the sample in the organic phase was thenintroduced into the glass tube using a syringe and the solvent waseliminated using a vacuum pump or air compressor. The target analytesthen were transferred into the PDMS needle trap using a sampledisplacement approach at 300° C. for 5 min with a purging flow rate of30 ml/min. The GC conditions for the separation are shown in Table 4,while the total ion chromatograph of the separation is seen in FIG. 17 ,which clearly shows that high molecular weight, high-boiling PAHs suchas benzo perylene and benzo fluoranthene have been separated anddetected.

TABLE 4 Sample Delivery Needle Trap Injection Type Splitless withpre-run split closed Injector Temperature 290° C. Transfer LineTemperature 270° C. Trap Temperature 190° C. Initial Temperature/HoldTime 50° C. for 10 s Temperature Ramp Rate 2° C./sec FinalTemperature/Hold Time 300° C. for 150 s

This portable GC/MS technology of the first embodiment may also be usedas a general screening tool for SVOCs in water using micro liquidextraction (MLE) and a coil wire filament (CWF). The experiments werecarried out using tap water spiked with SVOCs at concentrations from lowppb-sub ppm levels. A small amount (0.2-0.5 mL) of suitable solvent,such as dichloromethane, hexane, pentane or acetone is used forextraction. Manual shaking and salting-out may be applied using NaCl at0.5-3% to speed up the extracting process. The extraction is performedfor a few minutes, the solvent containing the analytes then applied onto the coil or if necessary, concentrated by letting the solventevaporate after transferring to a small vial. Sample introduction usingthe coil is performed after solvent on the coil is evaporated. Thescreening tests were carried out with mixtures of PAHs, phenoliccompounds, phthalate esters, organo-chloride, organo-phosphorus andpyrethroid pesticides and herbicides. However, as has been previouslyshown, the separation of PAHs and various pesticides will only showrepresentative data for the phenolic compounds and the phthalate esters.The chromatographic separation conditions for the phenols and phthalateesters are shown in Table 5. Table 5 shows the chromatographicseparation conditions for the screening of 9 phenolic compounds, 6phthalate esters. An additional 14 general pesticides, 6 herbicides and10 insecticides were screened using similar conditions.

TABLE 5 GC Parameter Phenols Phthalate Esters Sample Delivery Coil WireFilament Coil Wire Filament Injection Injection Injection TypeSplit/Splitless Split/Splitless Injector Temperature 290° C. 300° C.Transfer Line 270° C. 280° C. Temperature Trap Temperature 200° C. 200°C. Initial Temperature/Hold 50° C. for 10 s 50° C. for 10 s TimeTemperature Ramp Rate 2° C./sec 2° C./sec Final Temperature/Hold 200° C.for 60 s 300° C. for 60 s Time

FIG. 18 shows the total ion chromatogram of the separation of all thephenolic compounds in water, with phenol (C6H5OH) identified with thebold red arrow. The extracted ion chromatogram of phenol is shown on theright with the reference mass spectrum from the NIST library below it.The full suite of phenols identified from left to right are (1) phenol(2) 4-methyl phenol, (3) 2-nitro phenol, (4) 3,5-dichloro phenol, (5)4-chloro-3-methyl phenol, (6) 2,4,6-trichloro phenol, (7) 4-nitrophenol, (8) 2-methyl-4,6-dinitro phenol, and (9) pentachloro phenol.

The group of phthalate esters is shown in FIG. 19 , with dimethylphthalate (C10H10O4) shown with the bold red arrow. The extracted ionchromatogram of dimethyl phthalate is shown on the right, with thereference mass spectrum from the NIST library below it. The full suiteof phthalate esters identified from left to right are (1) dimethylphthalate, (2) diethyl phthalate, (3) dibutyl phthalate, (4) benzylbutyl phthalate (5) di-iso-octyl phthalate and (6) di-n-octyl phthalate.

The total running time for these screening tests for both phenols andphthalate esters, was less than 3 min. Ion molecule chemistry occurredto some degree on both types of samples, so absolute identification wasconfirmed using the NIST library search capability. Although the peakcapacities are relatively low for these separations, the deconvolutionalgorithm helped to separate and identify the analytes with greateraccuracy. Dynamic ranges and detection limits in real samples will bedetermined and presented in a future study.

There is a growing demand for the analysis of trace levels of volatileand semi-volatile organic compounds in air, water and solid matrixsamples under harsh conditions in remote, field-based locations. Thisstudy has demonstrated that it is now possible to achievelaboratory-grade performance with a portable GC-MS combined with rapidsample preparation/introduction techniques. This combination enables awide variety of environmental-based assays for both quantitative andqualitative screening purposes, which can provide fast, actionable datafor non-technical and inexperienced operators in the field.

It has been demonstrated that the technology used in this study of thefirst embodiment has detected SVOCs relevant to terpenes, plantprotection chemicals, and polycyclic aromatic hydrocarbons (PAHs), withvery high temperature boiling points (up to 550° C.), at low pptconcentrations in under 10 minutes total analysis time. It has alsoshown the detection of natural compounds such as geosmin can be detectedin water at low ppt levels. In addition, the screening of phenoliccompounds and phthalate esters in drinking water can be carried out atlow ppb levels. As a result, the employment of portable GC/MS andassociated sampling techniques provide the required sensitivity,selectivity, and speed of analysis for the effective analysis ofhigh-boiling-point SVOCs in the field.

Those skilled in the art will readily appreciate that many modificationsare possible in the example embodiments without materially departingfrom this first embodiment or the invention. Accordingly, all suchmodifications are intended to be included within the scope of thisdisclosure as defined in the following claims. It is the expressintention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6for any limitations of any of the claims herein, except for those inwhich the claim expressly uses the words ‘means for’ together with anassociated function.

What is claimed is:
 1. A heating system for a chromatography system, theheating system comprising: an inner ring; a heating wire woundcircumferentially around the inner cylindrical ring; a middle ringdisposed around the heating wire and the inner ring, wherein the heatingwire is in contact with an inner surface of the middle ring, wherein theheating wire is enclosed between the inner ring and the middle ring; achromatography column disposed circumferentially and in a single layeraround and in contact with an outer surface of the middle ring; and anouter ring disposed circumferentially around the chromatography columnand the middle ring.
 2. The heating system of claim 1 wherein theheating wire is wound circumferentially around the inner ring aplurality of times.
 3. The heating system of claim 2 wherein windings ofthe heating wire are equally spaced apart.
 4. The heating system ofclaim 2 wherein windings of the heating wire are in contact with oneanother.
 5. The heating system of claim 1 wherein the outer surface ofthe middle ring is substantially smooth such that the chromatographycolumn makes continuous contact therewith.
 6. The heating system ofclaim 1 further comprising a temperature sensor on the inner ring. 7.The heating system of claim 1 wherein a diameter of the outer ring is 10cm or less.
 8. The heating system of claim 1 wherein first and secondwings extend away from the outer ring.
 9. The heating system of claim 1wherein the outer ring comprises a plurality of tabs that are foldedaround the inner ring.
 10. The heating system of claim 1 wherein theinner ring is formed of aluminum.
 11. The heating system of claim 1wherein the middle ring is formed of aluminum.
 12. The heating system ofclaim 1 wherein the outer ring is formed of aluminum.